1, light safety classification
In general, light safety can be divided into the following two categories, namely, photobiological safety and interference light.
Light biosecurity
The main research areas of this type of light safety include UV, infrared, blue and visible radiation damage to human tissue. Common photobiological hazards are mainly photochemical UV damage to human skin and eyes, blue light on the human body retina damage, infrared laying on the eyes of the hazards and the impact of light and heat on the skin and so on.
In all the sensory organs of the human body, the eye is the most important part of its self-repair ability is relatively weak, once the outside of the optical radiation will cause irreparable damage to the eyes, even if the visible light may hurt people Eyes, such as short wavelengths of blue light can cause damage to the retinal photoreceptor cells, severe cases may cause degradation of pigment epithelial function, and if the higher intensity of radiation can cause retinal heat injury.
Interference light
Interference light is divided into two kinds of directness and indirectness. The former refers to the visual resolution caused by the luminous body with high brightness in the field of view. The latter means that the luminous body does not appear directly in the field of view, but the light projection Object surface reflection into the human eye after the problem.
Through some of the domestic led display manufacturers to investigate and found that led display the maximum brightness of 6 000 ~ 8 000 cd / m2, the value does not meet the minimum value of light biosafety brightness, we can see, led display And will not cause the human retina, including Blu-ray hazards, including photobiological hazards. In view of this, the following focus on the led display interference light problem analysis.
2, led display interference light formation reasons
personal reasons
led display with high brightness characteristics, if the display in the dark night brightness output to 8000 cd / m2, then it will cause serious light interference.
Location reason
The closer the observer is to the display screen, or the greater the pair of corners formed by the station position and the display screen, or the closer the observer's line of sight is to the orientation of the display, resulting in more severe interfering light.
Illumination reason
Day and night ambient illumination there is a significant difference, which also caused the same brightness led display in different periods of time will produce different degrees of interference light.
Observer reasons
Observers age, occupation, health status, psychological mood, will feel different degrees of interference light. Such as, often contact with photosensitizer or eye disease with the observer, will be more sensitive to light.
The content shows the reason
If the image content displayed on the display screen is too fast, it will cause the discomfort of the observer. The color brightness is too high, the transition will be blunt, and the human eye will be disoriented.
Criteria for evaluation criteria
The display screen is used in many places, such as road traffic, commercial areas, residential areas, etc., due to the nature of the site, the interference light evaluation criteria are also different.
Environmental reasons
Environmental conditions will be a significant impact on the display interference light, if the environmental conditions are more harsh, such as encounter haze, dust, fog, rain, wind and other weather, it will affect people to judge the interference light, Under the influence of external factors, it will cause the judgment standard to be inaccurate and affect the objectivity of the evaluation.
led display light pollution problem solution
led display high brightness characteristics of light pollution is an important reason, in order to effectively solve the problem of light pollution, can take the following security measures.
1, relying on the environment to adjust the brightness
Adjust the brightness of the human eye comfortable
According to the display in the ambient light intensity level, the overall brightness of the led display to adjust, to ensure that the display clarity at the same time, to avoid the dazzling, garish bad visual experience. Through the investigation and study shows that if the human eye habits 800 cd / m2 ambient brightness, then the human eye can see the brightness of 80 ~ 8 000 cd / m2, if beyond the brightness scale, the human eye must be a few seconds after conditioning to gradually see The Therefore, led display to rely on the environment to adjust the brightness, the introduction of environmental brightness monitoring equipment for the brightness adjustment to provide a reliable basis for the display brightness can be adjusted to the human eye comfortable viewing range. During the night, the brightness of the display should be controlled below 10 times the ambient brightness.
Introduced brightness adjustment standard
Many outdoor display to the night the brightness is too high, causing a serious light pollution, to the surrounding residents to bring a certain degree of life. To this end, the relevant departments should introduce the display brightness adjustment standards to strengthen the prevention and control of light pollution, requiring the use of the display unit must be based on the brightness of the environment to adjust the brightness of the output, strictly prohibited in the dark night output high brightness light.
2, reduce the blue light output
Different wavelengths of light on the human eye will bring different visual perception, because the human eye perception has a certain complexity, it is difficult to reflect the brightness of the human eye to reflect the light perception, it can introduce the amount of radiation indicators, As a criterion for judging the safe energy range of visible light. In measuring the role of light on the human eye, the human eye can not only feel the brightness of the blue light, but to introduce the irradiance measurement equipment, measured with the measurement equipment to objectively reflect the blue light output intensity of visual perception The led display manufacturers to ensure that the display on the basis of the display function, the appropriate reduction in Blu-ray output, so as to avoid discomfort to the human eye.
3, control the light distribution
Reasonable layout led display of light, in the human eye within the scale of the scale, evenly distributed display the output of the light energy, to avoid the display of local strong light problem. This requires the production of led display, the direction of the light must be irradiated and the scale of radiation to be strictly limited in order to achieve effective control led display light pollution purposes.
4, express security measures
In the led display product manual, to indicate the safety precautions, focusing on the brightness of the monitor display the correct way to explain the long-term vision of the human eye can show the possible damage. If the display brightness automatically adjusts the system running fault, you can use the manual adjustment of the way to adjust the brightness. At the same time, but also to the public universal light pollution safety measures to enhance the public self-protection capacity. Such as, can not look directly into the display, try to avoid the human eye focus on the screen details of the screen, to avoid the LED gathered in the fundus and cause visual bright spots, serious even on the retina brought burns.
5 to improve product performance and quality
In order to ensure the performance of led display products, products should be strengthened in the indoor and outdoor environment in the brightness detection. In the indoor testing process, the staff to wear the brightness attenuation of 2 to 4 times the black sunglasses, in the near range to observe the details of the display screen is a problem. In the outdoor testing process, the staff to wear the brightness attenuation of 4 to 8 times the black sunglasses. Especially in the dark environment to carry out testing work, the staff must wear safety tools, so as to avoid the staff exposed to light.
6 Introduce advanced technology
led display at different times, different locations of the brightness changes in the environment there are significant differences. Once the display brightness output exceeds the ambient brightness of 60%, it will bring discomfort to the human eye, resulting in light pollution. Therefore, the LED display should be equipped with outdoor brightness collection system, real-time collection of environmental brightness, and environmental brightness information transmitted to the central control room, the central control room according to the received data information, automatically calculate the most appropriate display output brightness , And as a basis for brightness adjustment.
In addition, the led display should be introduced multi-level gray-scale correction technology to improve the ordinary 8-bit color display color transition blunt problem, to avoid the eye to bring a strong discomfort. In the multi-level gray-scale correction technology support, the original display system color display level to 14 bit, so as to bring a gentle eye color transition, reduce the light on the human eye stimulation.
Conclusion
In summary, led display as a light source, in the course of the operation will inevitably be light and light pollution problems, in order to effectively prevent the lead display on the human body harm, should be a comprehensive analysis of its light safety issues On the basis of reasonable and feasible measures to eliminate the led display light pollution, which in addition to providing protection for human health, but also for the extended range of LED display applications to help.